如何在macOS的Bash中将softwareupdate --list的输出保存为变量？

Issues with Your Original Approach #

Your command fails to capture the full output for two key reasons:

• Missing stderr capture: softwareupdate --list sends some output (like the "No new software available" line) to stderr instead of stdout. The $(...) substitution only captures stdout, so those lines are lost.
• Word-based splitting: Assigning to an array with updates=( $(command) ) splits the output into individual words (using whitespace as the delimiter), not entire lines. Blank lines are ignored, and lines with spaces get split into multiple array elements.

Correct Method to Capture Full Output #

Step 1: Capture Both Stdout and Stderr, Read Lines into Array #

Use readarray (or mapfile, its equivalent) to read each line of the command's output (including stderr) into an array. This preserves line breaks and keeps each line as a single array element.

readarray -t updates < <(softwareupdate --list 2>&1)

• 2>&1 redirects stderr to stdout, ensuring all output is captured.
• -t removes trailing newline characters from each line.
• The process substitution <(...) feeds the command's output directly into readarray.

Step 2: Print the Full Captured Output #

To display the entire output correctly, use printf to print each array element on a new line:

printf '%s\n' "${updates[@]}"

• "${updates[@]}" expands to each element of the array, preserving spaces and special characters in individual lines.
• %s\n ensures each element is printed followed by a newline, matching the original command's output format.

Alternative for Older Bash Versions #

If readarray isn't available (bash < 4.0), use a while loop to read lines into the array:

updates=()
while IFS= read -r line; do
    updates+=("$line")
done < <(softwareupdate --list 2>&1)

Then print the output with the same printf command as above.

内容的提问来源于stack exchange，提问作者user2416805